Sensitive,quick response ionization chamber



Feb. 25, 1969 R. TAYLOR 3,430,087

SENSITIVE, QUICK RESPONSE IONIZATION CHAMBER Filed NOV. 4, I966 INV ENTOR RANDOL PH 6. TAYLOR BY flfi Z fiwwb AGENT m ATTORNEY United StatesPatent f 1 Claim ABSTRACT OF THE DISCLOSURE This invention is directedto an ionization chamber having a cylindrical anode with an axiallydisposed wire electrode operable for detection of ionizing radiation ina range of from about 0.5 to about 8.0 angstrom units with a fastrecovery. Fast response is brought about by modification of the cathodeto include vane-like screen structures secured thereto by brazing,welding, or any other suitable manner. The vane-like structures extendradially out from the cathode with their outer edges spaced from theanode. The tube is provided with a gas filling of krypton or argon witha beryllium window through which the ionizing radiation enters thechamber.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The present invention relates to ionization chambers and moreparticularly to an improved ionization chamber which has a fast responsetime.

In general, conventional ionization chambers comprise two electrodes ina surrounding of a desired gas at a desired pressure. Radiation enteringthe ionization chamber ionizes the gas molecules therein to produceions. The negatively charged ions produced will travel to the anodewhereas the positively charged ions travel in the opposite direction tothe cathode. The resulting output of the tube is a measure of theintensity of the ionizing radiation which enters into the ionizationchamber.

Heretofore, ionization chambers have been used in a stationaryenvironment and also mounted upon rotating rockets or satellites andfired into the atmosphere. Ionization chambers fired into the atmosphereon a rotating rocket or satellite responds to incident radiation eachrevolution of the rocket and should respond sufiiciently fast that thepeak signal of one event is telemetered to a ground station prior to aresponse from any succeeding event due to radiation excitation.Ionization chambers used heretofore are slow in their response time andtherefore when mounted on a rotating rocket, the signal of one event issuperimposed on the output of the succeeding event thereby giving afalse signal. Normally, satellites in order to obtain desired stability,rotate at a revolution of from 2 to 3 revolutions per second. The priorart ionization tubes operate satisfactorily at about one revolution persecond. Thus, for good operation of the prior art tube the rocketspinning rate must be reduced to at least one revolution per second orlower; however, at one revolution per second the rocket misbehaves anddoes not follow the intended flight pattern.

The ionization tube of the present invention overcomes the drawbacks ofthe prior art ionization tubes by modification of the cathode whichenables one to measure radiation in a range from about 0.5 to about 3.0angstrom units depending on the type and thickness of the window, andthe gas filling within the tube. This ionization tube operatessatisfactorily even at a rotational rate of about 5.0 revolutions persecond of the rocket.

3,430,087 Patented Feb. 25, 1969 ice It is therefore an object of thepresent invention to provide an ionization tube which has a quickresponse time.

Another object is to provide an ionization tube which will operatesatisfactorily for rockets spinning at a spiiining rate up to at least 5revolutions per second.

Still another object is to provide an ionization chamber which issatisfactory to study solar radiation by use of spinning rockets orsatellites.

Yet another object is to provide an ionization chamber useful on arocket for upper air research in determining radiation in a range offrom 0.50 to 3.0 angstrom units and from 2.0 to 8.0 angstrom units.

Other objects and advantages will be apparent to those skilled in theart upon the consideration of the following description and the attacheddrawing, wherein:

FIG. 1 is a cross-sectional view of a preferred embodiment of theinvention; and

FIG. 2 is a cross-sectional view taken along the lines 22 through FIG. 1which illustrates the relationship of the radial metallic extensionssecured to the cathode.

The improvement in ionization chambers illustrated by the presentinvention is brought about by securing equiangularly spaced thinmetallic radial vane-like collector surfaces to the cathode. Thecollector surfaces may be formed of screen material and welded or brazedto the cathode along the entire length thereof. Thus, the addition ofthe screen collector surfaces allows the electric field produced by apotential of 50 to volts to be extended throughout the volume of thetube resulting in a faster response.

Now referring to the drawing, wherein like reference charactersrepresent like parts throughout the figures, there is shown byillustration an ionization chamber made in accordance with the presentinvention. As shown, FIG. 1 illustrates a cylindrical housing ofstainless steel or any other suitable metal which is closed at one endand open at the opposite end. The cylindrical housing forms the anode 11which surrounds an axially disposed cathode 12 such as a Wire or rodwhich is insualted from the anode structure by any suitable means 13.Secured to the cathode by welding, brazing, or any other suitable methodare four equi-angularly spaced wire mesh collector surfaces 14 whichextend along the entire length of the cathode wire. The wire meshcollector surfaces 14 extend toward the inner surface of the anode inspaced relationship therewith with their edges parallel with the anodesurface. The bottom edge of the wire mesh collector surfaces extendsdownwardly to the insualtor 13 and rests thereon such that the loweredge of the collector surface is spaced from the enclosed end of theanode. The open end of the anode structure is closed by a radiationpermeable window 15 which may be secured over a wire mesh supportstructure 16 which prevents the window from being pulled in when thetube is evacuated. The window may be made of beryllium having athickness of about 5 mil to about 50 mil. The window is sealed within ashoulder 17 in the anode in a vacuum tight relationship by any suitablesealant and the tube is evacuated to a desirable pressure and filledwith a gas depending on the wave length range to be detected.

In making a tube having an anode of about one inch in diameter with acathode of about one inch in length for the detection of radiationhaving a range of about 0.50 to about 3.0 angstrom units, the gasfilling in the tube should be krypton. The tube is evacuated throughtube 21 to a pressure of 10 millimeters of mercury and a gas filling ofkrypton is injected into the tube to a pressure of 1520 millimeters ofmercury at 0 centigrade. The window is formed of a 50 mil beryllium. Inorder to produce an ionization tube for detection of radiation in arange between about 2.0 and about 8.0 angstrom (LP)(273+RT) AP=adjustedpressure LP=list pressure given for tube filling at centigrade RT=roomtemperature in degrees centigrade.

In operation of the tube for detecting radiation in the range givenabove, the tube is formed as described above with the listed gaspressures with a window of the dimensions given. Ionizing radiationpasses through the window into the area confined by the anode therebyionizing the gas therein. The positive ions are drawn toward thevanelike structures attached to the cathode and the negative ions aredrawn to the anode structure. Since the vane-like structure attached tothe cathode extends outwardly from the cathode to a close tolerance withthe anode it can be seen that the ions directed toward the cathode willstrike the cathode surface much faster than in a tube which is notprovided with the vane-like structure. Thus, all of the ions confinedwithin the anode structure will be directed to the cathode structure ina much faster time which will result in producing an output inaccordance with the incident radiation. Thus, when the tube ispositioned on a rocket which is fired into the upper atmosphere androtates as the rocket moves through the upper atmosphere, the tube, asdescribed above, will operate with sufficiently fast response that therotational rate of the rocket may be at least revolutions per second.The tube, as described above, will have a suificiently fast responsetime that the peak output will be reached before the rocket hascompleted its revolution wherein the tube will have passed through itspeak output and back down to its normal state wherein it is ready toreceive additional ionizing radiation and give an accurate measure ofthe intensity of the radiation. Thus, a tube made as described abovewill not permit a signal from one ionizing event to be superimposed onthe signal of another or any succeeding event.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claim the invention maybe practiced otherwise than as specifically described.

What is claimed and desired to be secured by Letters Patent of theUnited States is:

1. A sensitive, quick response, ionization chamber which comprises:

a cylindrical metallic anode closed at one end and open at the oppositeend to form a housing,

a cathode,

said cathode extending through said closed end of said anode on andalong the axis thereof and insulated therefrom,

a plurality of equi-angularly spaced radially extending vane-likestructures secured electrically to said cathode, extending along thelength thereof within said housing and spaced from said anode,

a window through which radiation enters into said ionization chamber,

said window enclosing said open end of said anode,

said window being formed of beryllium with a thickness of from about 5mil to about mil in thickness,

an ionizable gas filling in said ionization chamber selected from thegroup consisting of argon and krypton,

said gas filling having a pressure of from about 760 to about 1520 mm.of mercury,

whereby said ionization chamber operates for detection of radiation in arange from about 0.50 to about 8.0 angstrom units.

References Cited UNITED STATES PATENTS 2,566,089 8/1951 Linder 313-932,599,352 6/1952 Schneider 31393 2,604,600 7/1952 Neufeld 313932,648,781 8/1953 Herzog et al. 31393 2,837,656 6/1958 Hendee et al.31393 2,874,304 2/ 1959 Lichtenstein 313-93 2,951,942 9/ 1960 Kramish250- 83.1 3,219,869 11/1965 Schmidt 313-93 3,322,991 5/1967 Sterk et a1313-93 JAMES W. LAWRENCE, Primary Examiner.

R. F. HOSS-FELD, Assistant Examiner.

US. Cl. X.R. 313-184, 217

